> Well, sabotage could also have been done by the other side, to point out the russian incompetence and drive them out even earlier, but the risk/reward does not make this likely.

1. NASA wants Russia to maintain a presence on the ISS. Many of the necessary functions for operating the ISS are spread across both the US (international) and Russian sides. If the Russians left, that would dramatically complicate operations.

2. How would the US even get to the spacecraft in question? It's not like someone could casually take a stroll around the station and pop in a hole with a drift and hammer.

3. Even if the US could access the spacecraft in question, it's not obvious to me that US Astronauts would actually do the deed instead of blowing a whistle. It's not like they're CIA operatives. There's a great deal of camaraderie between the personnel of each side.

NASA isn't in the business of sabotaging, that would be the CIA. That means that

1. NASA cares about keeping the ISS alive, the CIA might have other priorities and care more about how this humiliates Russia much more than NASA

2. I would be more surprised if there were no CIA agents in the manufacturing pipeline of Soyuz spacecraft, never mind the launch site. Just strategically weaken some parts so they fail in orbit.

3. So let's use CIA operatives

I'm not saying it was the CIA. The CIA has motive and capability to do it. But it could as well be Russian corruption somewhere in the supply chain, or just bad luck

Seems like a pretty wacky thing to do IMO.

Maybe the CIA does have some operatives in the Russian aerospace industry. But why would any such operatives risk exposing themselves by sabotaging hardware going to the ISS? Just for a rather contrived plan to make the Russians look incompetent while putting American astronauts at risk too? Surely the CIA can come up with better ways to make the Russians look incompetent without putting carefully established agents at risk. Or they can just do nothing, since the Russians seem to have little trouble displaying ineptitude without any assistance.

Seems unlikely, There's little to gain from this. There are far larger propaganda victories already that actually matter to the populace.

4. The Soyuz that had the first coolant leak had an American astronaut on board. Why would the US risk its own people?

That seems like the weakest argument against it. If we're talking about the kind of shadowy secret agents who will sabotage a $150 billion project (most of which was paid by their own side) as a manoeuvre in a complicated geopolitical game, surely they're not above sacrificing a few innocent lives for it.

Sabotage might also be performed by a disgruntled / disturbed worker, not working for either 'side'.